1. Field of the Invention
The present invention relates to an optical recording apparatus, and in particular to an optical recording apparatus in which a semiconductor laser array including a plurality of light emitting parts is employed as a recording light source.
2. Description of the Prior Art
Heretofore, there has been proposed an optical information recording apparatus in which information such as characters, numbers or figures, graphic patterns or the like can be recorded on a recording medium at a high recording speed by using for the recording light source an array of plural semiconductor lasers. A typical example of such a recording apparatus is shown in FIG. 1. Referring to the figure, the light source is constituted by an array 20 which includes a plurality of semiconductor lasers 21.sup.(1), 21.sup.(2), . . . , 21.sup.(N) adapted to be driven separately be respective current supply circuits 23.sup.(1), 23.sup.(2), . . . , 23.sup.(N) (which will be referred to collectively as a drive circuit 24 for the convenience'sake of description). The operation modes of the semiconductor lasers depend on the lasing control signals applied to the input terminal P.sub.in of a character generating circuit 26. For example, when the lasing control signal for a certain one of the semiconductor lasers is logic "1," the current supplied thereto from the associated current supply circuit will be interrupted to stop the lasing of that laser. On the other hand, when the lasing control signal is logic "0," then a drive current of a magnitude I corresponding to a laser output of a predetermined level is supplied to the associated semiconductor laser. The logic levels "1" and "0" of the lasing control signal input to the terminal P.sub.in of the character generating circuit 26 are determined by the shapes of a character or pattern to be recorded. Usually, such a lasing control logic signal is available from a computer system to which the optical recording system is associated.
Output beams 22.sup.(1), 22.sup.(2), . . . , 22.sup.(N) from the semiconductor lasers modulated by the respective control signals are projected onto a surface of a photo-sensitive recording medium 11 through a lens 40 in a row of magnified beam spots. More specifically, the laser beams passed through the lens 40 impinge on a reflection face 4' of a polygonal mirror 4 which is rotated by a motor 70, whereby each of the reflected laser beams 8.sup.(1), 8.sup.(2), . . . , 8.sup.(N) is projected onto the recording medium 11 in a sector-like scanning manner. A synchronizing signal generator 30 is provided to assure synchronization among the rotation of the polygonal mirror 4, the operation of a drive source 10 of a feeding mechanism 10' for the photo-sensitive recording medium 11 and the operation of the laser beams effected by the drive circuit 24 modulating the semiconductor lasers. The motor 70 for rotating the polygonal mirror 4 is driven by a drive source 71 which is controlled by the synchronizing signal generator 30.
In the optical information recording apparatus of the arrangement outlined above, the individual laser beam emitting parts (or light emitting points) of the semiconductor laser array 20 used as the light source are usually arrayed as close as possible to one another with a view to accomplishing a high recording density as well as a high recording speed. For example, the light emitting points may be disposed in juxtaposition to one another with an extremely small distance on the order of 10 .mu.m. However, such a close arrangement of the individual light emitting points will undesirably involve unstable operation of the semiconductor laser array due to heat generated in the laser beam emitting portions. Thus, in order to assure a stable operation of the semiconductor laser array of the hitherto-known optical information recording apparatus, the distance among the light emitting points has to be correspondingly increased, which in turn means that the distance between the light spots on the recording medium is correspondingly increased, making it difficult to attain the high recording density and hence the high recording speed.